In the field of telecommunications, voice services such as the ubiquitous telephone service, also known as Plain Old Telephone Service (POTS), have been provisioned using circuit-switched technologies over a circuit-switched infrastructure. Other services provisioned using circuit-switched technologies include, but are not limited to, facsimile transmission and video conferencing.
The benefits provided by the circuit-switched infrastructure stem from a very high Quality-of-Service enabled by the reservation of a specific amount of bandwidth for each established connection end-to-end and the use of hot standby bandwidth to ensure minimal exposure to circuit-switched infrastructure failures. The circuit-switched infrastructure includes main and hot standby equipment, and main and hot standby interconnecting trunks.
The drawbacks come from huge costs incurred deploying, maintaining, modifying, etc. the redundant circuit-switched infrastructure. Another drawback comes from an inefficient utilization of the reserved bandwidth particularly accentuated by the fact that the reserved hot standby bandwidth is not intended to ever be used. If human voice is conveyed during a telephone session, which represents the most extensive use of circuit switched technologies, up to 60% of the reserved main bandwidth is also wasted as the human voice has an activity factor of 0.4. Facsimile and video conference services have a much higher activity factor.
In the field of telecommunications, data services are being provisioned using packet-switched technologies over a packet-switched infrastructure. Packet-switched technologies provide bandwidth utilization efficiencies at reduced equipment, deployment, maintenance, etc. costs. However, without reserving bandwidth and without using a redundant infrastructure, packet-switched technologies only provide best-effort transport of data. Resiliency to packet-switched infrastructure failures is typically built-in as Protocol Data Units (PDU) including packets, frames, etc. are routed in transit at intermediary network nodes in the transport path between connection end-points. Service provisioning typically does not benefit from a high QoS.
Recent packet-switched technology advances include Asynchronous Transfer Mode (ATM) and MultiProtocol Label Switching (MPLS) packet-based technologies which address the typical QoS issues mentioned above.
ATM in particular uses fixed size PDUs, known as cells, to convey data payloads in an ATM network with enforced data traffic constraints providing a high QoS. The combined benefits of a high QoS data transport and reduced deployment and maintenance cost of the ATM infrastructure, make ATM technologies a good candidate in provisioning voice services over packet-switched infrastructure. And, there is pressure to migrate voice services, currently provisioned over circuit-switched infrastructure, over to packet-switched infrastructure.
The provisioning of voice services over packet-switched infrastructure is a current topic of intense research, and development. However, solution deployment is not as extensive as expected. The biggest hurdles to overcome in migrating traditional voice services to packet-switched infrastructure, have to do with the fact that the local loop infrastructure, which represents the largest portion of circuit-switched infrastructure, always has, and still typically provides analog signal transport only. Local loops are dedicated pairs of copper wires connected to a local exchange telephone switch, also known as a Service Switching Point (SSP), at one end, and at the other end, to a telephone jack at a customer's premises. The local loop infrastructure has changed very little since the initial deployment of telephone services. Changes to the extensive local loop infrastructure are prohibitive in terms of cost.
Attempts have been made at adapting local loop infrastructure to support digital data transport however Digital Subscriber Line (DSL) solutions suffer from a limited reach and incur large deployment costs. To date the deployment of DSL services have concentrated on Internet service provisioning within a limited distance from the local exchange telephone switch where DSL deployment costs may at least be recovered in part.
With the advent of the digital telephone exchange, the circuit-switched technology of today provides for the digitization of the analog audio signal at digital local exchange telephone switches, and for redundant digital signal transport over the redundant circuit-switched infrastructure using Time Division Multiplexing (TDM) technologies. The provision for analog-to-digital conversion is a plus in migrating circuit-switched voice telecommunications services to packet-switched infrastructure. Some bandwidth utilization efficiencies may be taken advantage of.
Making reference to FIG. 1, current voice services are typically provided from a POTS termination 102, over a local loop 104, via a digital exchange SSP 106. Analog audio signal conversion to a digital TMD signal conversion is performed on the customer side of the SSP 106.
Connection control and TDM signal transport, from the SSP 106 and over the Public Switched Telephone Network 110, is provided via a layered infrastructure.
A connection control layer includes signaling links 122, and a connection controller, also known as a Signal Control Point (SCP) 120. The connection control layer uses packet-switched technologies to process packetized signaling messages known as the Signaling System 7 (SS7) protocol.
The TDM signal transport layer includes redundant TDM signal transport trunks 112, and a hierarchy of redundant circuit-switching equipment including, but not limited to, local exchanges 106 and tandem exchanges 116. The tandem exchanges 116 form a layered hierarchy typically mimicking government jurisdictional associations (only one layer of the hierarchy is shown). Each local exchange SSP 106 is also know as a Class 5 switch, while the tandem exchanges 116 are also known as Class 4 switches.
The redundant TDM trunks 112 come in a variety of transport capacities including: T1/DS-1, a North American Standard trunk providing for the time division multiplexed conveyance of 24 digitized voice signals; E1, an European Standard trunk providing for the time division multiplexed conveyance of 32 digitized voice signals; and multiples thereof.
In establishing a connection end-to-end, a POTS termination 102, goes off-hook, analog dialing signals conveyed over the local loop 104 are interpreted by the SSP 106, the SSP 106 sends an SS7 connection request over a signaling link 112 to the connection controller SCP 120, SCP 120 determines the destination POTS termination 102 across the Public Switched Telephone Network PSTN 110, sends SS7 setup signaling messages over signaling links 122 to a determined group of telephone exchanges including the end SSPs 106 and intermediary redundant tandem telephone exchanges 116.
Once the setup signaling messages are interpreted and redundant resources are reserved, the SSP 106 associated with the destination POTS termination 102 is instructed to apply a ring signal on to the local loop 104 associated with the destination POTS termination 102.
Once the destination POTS termination 102 picks up, the SSPs 106 digitize audio signals received over respective local loops 104 and the resulting digitized audio signals are sent over the redundant reserved infrastructure in the PSTN 110 between the SSPs 106. Each digitized audio signal received at an SSP 106 is played back, in analog form, over a corresponding local loop 104.
Current research and development has enabled the substitution of much of the expensive redundant circuit-switched digital signal transport infrastructure in the core of the PSTN 110 with a packet-switched data transport infrastructure. FIG. 2 is a schematic diagram showing an exemplary deployment using ATM packet-switched technology and equipment.
An ATM data transport network, as shown at 210, includes ATM nodes 206 and interconnecting links 204. The ATM infrastructure of the ATM network 210 is managed by a Network Management System (NMS) 230. In particular, the NMS 230 monitors every aspect of the entire ATM infrastructure under its realm of management including: link status, network node status, available transport bandwidth, reserved transport bandwidth, available processing bandwidth, etc. Connection control in the ATM network is provided via a Connection Manager (CM) 240 associated with the NMS 230. The connection manager 240 instructs ATM network nodes 206(216) to establish data connections based on connection requests received from edge network nodes 250.
Data and ATM Private Network-Node Interface (PNNI) signaling messages are conveyed employing fixed size cells. Each cell carries a payload of 48 bytes.
In order to provide transport of voice service digital signals, ATM technology development led to Media Gateway (MG) ATM network nodes 216 and the development of a Media Gateway Controller (MGC) 220.
Special physical layer equipment, referred to as circuit emulation equipment, implementing media gateway functionality is used to convey a TDM signal using ATM cells and conversely to extract and combine ATM cell payloads to regenerate a TDM signal. When circuit emulation equipment at a media gateway network node 216 is used for conveying TDM signals over the ATM infrastructure, the circuit emulation equipment receives connection control instructions from the MGC 220 associated with the connection controller 120 and not from the connection manager 240 associated with the NMS 230.
With the circuit emulation equipment configured to receive connection control instructions from the MGC 220, the MGC 220 uses signaling links 222 to instruct media gateway nodes 216 to request Permanent Virtual Circuit (PVC) connection establishment from the connection manager 240 as connections are needed over the ATM network 210. If Soft PVCs (SPVCs) are used, then on receipt of instruction from the MGC 220 to establish a connection, a media gateway node 216 collaborates with other ATM network nodes 206 via PNNI signaling to establish the connection without involving the connection manager 240. At all times, the NMS 230 retains the ability to monitor and configure the circuit emulation equipment and the media gateway nodes 216.
FIG. 3 is a schematic diagram showing interconnected network elements implementing connected data transport networks.
Network nodes 206, 216-A, 216-B are physically interconnected via physical links 204 in data transport networks 210. Data transport networks 210 may be bridged via bridge data network nodes 306 to enable data exchange therebetween. Connected data transport networks 210 can be grouped defining areas of focus and influence for the purposes of network management, known as network partitions 308.
All data network equipment is subject to design choices which are bound to be different from vendor to vendor. With regards to data network equipment, for example network nodes schematically shown in FIG. 3, an equipment vendor may chose to implement an integral device 216-B having a switching processor and a group of ports 312. Of particular relevance are network nodes 216-B having circuit emulation ports 312. Another equipment vendor may chose a customizable implementation of a network node 216-A including: a switching fabric, an equipment rack divided into shelves, each shelf 322 having slot connectors for connection with interface cards, each interface card 324 having at least one port 312. Of particular relevance are network nodes 216-B having circuit emulation interface cards 324 with at least one circuit emulation port 312. The two network nodes 216-A and 216-B provide the same cell switching function. The network node 216-A is better adapted to provide high throughput.
Media gateway network nodes 216 including circuit emulation equipment, when not operating as media gateways are managed by the NMS 230. The NMS 230 makes use of a containment hierarchy 400 shown in FIG. 4 for management thereof.
In configuring physical links 212 for TDM signal transport, to provision transport for voice services over cell-switched infrastructure, the connection control over the associated circuit emulation ports 312 must be relinquished to the MCG 220. The hand-over includes configuring of the relevant circuit emulation ports 312 to operate in accordance with the Internet Engineering Task Force (IETF) Megaco protocol specification, which is incorporated herein by reference. The International Telecommunications Union (ITU) H.248 media gateway protocol represents an exemplary implementation of the IEFT Megaco protocol, the specification of the ITU H.248 media gateway protocol is incorporated herein by reference.
Prior art techniques used in configuring respective circuit emulation equipment to operate in compliance with the H.248 media gateway protocol, include using an Element Management System (EMS) to manually connect to the media gateway network node 216, navigating through configuration prompts via manual prompt command line input, identifying each relevant circuit emulation interface card 324 and each circuit emulation port 312, and determining which DS1 channel of the corresponding physical link 212 is not in use, configuring DS1 channel operational parameters to enable H.248 protocol support, etc.
Performing these manual steps is very time consuming and error prone particularly considering that in configuring channelized circuit emulation ports 312, the configuration has to be performed for each DS1 channel associated with the circuit emulation port 312. Consider a typical deployment example wherein the circuit emulation port 312 is an Optical Carrier (OC)-3 port. Each OC-3 circuit emulation port 312 has a transport capacity divided into 84 DS1 channels each of which needs to be configured individually. Media gateway network nodes 216-A employ multiple circuit emulation interface cards 324, the aggregate of which implement dozens of OC-3 circuit emulation ports 312. Suppose an exemplary node 216-A has a dozen of OC-3 circuit emulation ports 312 designated to carry traffic for voice services—manual configuration of 84×12=1008 DS-1 channels needs to be performed. This amount of manual provisioning represents a huge entry barrier for migrating circuit-switched voice services over packet-switched infrastructure. Depending on the vendor equipment used, H.248 support may only be activated on a per-DS-0 channel basis which further compounds manual provisioning problems for the necessary large scale deployment.
Prior art developments attempting to alleviate this configuration drawback include the use of scripts to automate parts of the manual provisioning process. However, these attempts are limited typically to channel DS-1/DS-0 operational parameter changes. The selection of the relevant circuit emulation equipment, circuit emulation equipment components, and configuration contexts still being limited to manual work. Further automation through scripts is of little value given a typical diverse vendor deployment of network nodes 216-A/216-B in a network 210 as every vendor equipment has a different implementation of the command prompt interface for element management and requires the use of different element management systems.
There therefore is a need to reduce the huge entry barrier in configuring equipment to provide packet-switched transport for circuit-switched voice services.